Stuart Hebert of the Gentoo blog has posted this new item as a reminder to all of those naysayers out there that didn't think it could be done that PHP4 and PHP5 can live together happily on the same box.

Today has served as a timely reminder to me that not everyone understands that it's perfectly possible to have both PHP4 and PHP5 installed in Apache at the same time. A lot of folks just stop when they learn that you can't load mod_php4 and mod_php5 at the same time into Apache. There's no solution in the excellent PHP Manual that I could spot this afternoon (maybe I've just missed it?), and a lot of folks just don't get any further along than that.

As an illustration of its possiblity, he points to this article from Andreas Korthaus showing how it's done under various different types of installs (Apache/CGI, Aapche/suphp).